Anti-reflection (AR) coatings are known in the art. For example, AR coatings in the visible range are widely used on glass in electronics, lighting, appliances, architectural, and display applications. However, in many of these applications, tempered or heat-strengthened glass may be required. Tempering or heat strengthening of the glass is sometimes done prior to the deposition of the AR coating to avoid unwanted changes in the optical, mechanical, or aesthetic quality of the coating as a consequence of exposing the coating to the high temperatures required for tempering and other forms of heat treatment. However, this “temper then coat” method may be undesirable in certain circumstances. Thus, it will be appreciated that there exists a need in the art for improved AR coatings (e.g., temperable AR coatings) for coated articles such as windows and the like.
In certain example embodiments, coatings may suffer from a lack of durability, particularly after heat treatment and/or thermal tempering, due to a residual net tensile stress that is too high. A large enough net tensile stress in a layer stack may cause aesthetic degradation of the coating (e.g., cracking), especially after a heat strengthening and/or tempering process.
Those skilled in the art thus will appreciate that there also is a need for improved durability in anti-reflection coatings
In certain example embodiments of this invention, there is provided a method of making a heat treatable coated article comprising an anti-reflection coating, the method comprising: disposing a stress-reducing layer over and contacting a glass substrate, the stress-reducing layer having an index of refraction that substantially matches an index of refraction of the glass substrate; disposing a layer having a medium index of refraction over the stress-reducing layer; disposing a layer having a high index of refraction over the medium index layer; disposing a layer having a low index of refraction over the high index layer, where the index of refraction of the high index layer is greater than those of the medium and low index layers, and the index of refraction of the low index layer is less than that of the medium index layer; and wherein a net residual stress of the anti-reflection coating is compressive (e.g., following optional heat treatment).
In certain example embodiments of this invention, there is provided a method of making a heat treatable coated article comprising an anti-reflection coating, the method comprising: disposing a stress-reducing layer over and contacting a glass substrate, the stress-reducing layer comprising an oxide and/or nitride of silicon, and having an index of refraction that differs from an index of refraction of the glass substrate by no more than about 0.2; disposing a layer comprising silicon oxynitride over the stress-reducing layer; disposing a layer comprising an oxide of niobium over the layer comprising silicon oxynitride; disposing a layer comprising an oxide of silicon over the layer comprising an oxide of niobium; and wherein the index of refraction of the high index layer is greater than those of the medium and low index layers, and the index of refraction of the low index layer is less than that of the medium index layer, and wherein a net residual stress of the coating is compressive.
In certain example embodiments of this invention, there is provided a heat treatable coated article comprising: an antireflection coating supported by a major surface of a substrate, the substrate being heat treatable together with the antireflection coating, wherein the antireflection coating comprises, in order moving away from the substrate: a stress-reducing layer comprising a material having a compressive residual stress after heat treatment; a medium index layer comprising silicon oxynitride; a high index layer comprising an oxide of niobium, and a low index layer comprising an oxide of silicon, wherein the coating has a net compressive residual stress (e.g., following heat treatment).
In certain example embodiments of this invention, there is provided a heat treated coated article comprising: an antireflection coating supported by a major surface of a substrate, the substrate being heat treated together with the antireflection coating, wherein the antireflection coating comprises, in order moving away from the substrate: a stress-reducing layer comprising an oxide and/or nitride of silicon; a medium index layer comprising silicon oxynitride; a high index layer comprising an oxide of niobium, and a low index layer comprising an oxide of silicon, wherein the coating has a net compressive residual stress after heat treatment.
In certain example embodiments, the same or similar antireflective coatings may be provided on one or both major surfaces of the glass substrate.
The features, aspects, advantages, and example embodiments described herein may be combined to realize yet further embodiments.